Overview of the experimental setup. Photographs (a) and schematics (b) of a capacitively coupled coaxial cable and an aperture coupled rectangular waveguide. (c) Schematic of the room temperature setup using a vector network analyzer (VNA). A through-open-short-match (TOSM) calibration is used to account for loss and phase offsets in the interconnecting cables. (d) Schematic of the FPGA-based microwave setup  used for measurements at cryogenic temperatures.